Rotation responsive switch



June 17, 1969 A. RASCHKE 3,

ROTATION RESPONSIVE SWITCH Filed on. 1966 Sheet of 2 INVENTOR- HERBERTARASCHKE fmwnse'rw d TMSE'YQ ATTORNEYS Juhe 1959 H. A. RASCHKE 3,450,850

ROTATION RESPONSIVE SWITCH Filed Oct. 5, 1966 F/as INVENTOR. HERBERT ARASCHKE oumseml n! owns'eml A TTORNEYS US. Cl. ZOO-61.39 4 Claims ABSTRACT OF THE DISCLOSURE An electrical switch that establishes a circuit in response to rotation of a rotatable member in one direction and which interrupts the circuit when the rotatable member is stationary or is rotating in an opposite direction. The rotatable member has a cylindric surface; a convoluted spring is disposed around such cylindric surface throughout approximately a full 360 degree extent of the cylindric surface. The convoluted spring has a spiral portion extending from the portion that circumscribes the cylindric surface and the free end of such spiral portion is fixed to the case in which the rotatable member is supported so as to rotatably bias the spring. A contact point extends radially from the spring and a contact post is attached to the case and extends radially inwardly toward the movable contact point. The spiral portion of the spring biases the contact point away from the contact post until the cylindrical member rotates in the appropriate direction to move the point in a direction toward the post. Such direction tends to unwind the spring so as to permit relative movement between the cylindric surface and the spring.

This invention relates to a switch for completing an electrical circuit in response to rotation of a member, the switch being arranged to interrupt the electrical circuit when rotation of the member terminates. Although the switch has particular utility in connection with an electric backup alarm device used to produce a warning signal when a motor vehicle is moved in the reverse or backup direction, the switch is not to be considered limited to such structure.

In motor vehicles such as earth-moving trucks used around noisy construction sites, a sounder or alarm that signals movement of the vehicle in a reverse direction is frequently utilized to promote safety of those working on foot about the vehicle. Although alarms operating solely on a mechanical basis have been used with success in this connection, greater versatility and loudness can be obtained by providing an electrically operated reverse alarm system. Such electric alarm systems exist in the prior art as do mechanisms for actuating the alarm by completing an electric circuit thereto in response to reverse movement of the vehicle. By way of example, certain prior art systems employ a switch that is mounted to be actuated by gear shift linkage associated with the transmission of the apparatus. Such switches have various disadvantages including the need for frequent alignment and the fact that such devices are subject to premature failure because they operate in a highly dirty or contaminated environment.

The principal object of the present invention therefore is to provide a switch adapted to be connected to the speedometer outlet included on typical vehicle transmissions and which switch responds to the direction of rotation of such outlet so as to establish an electrical circuit when the vehicle is backing but not when the vehicle is moving forwardly or is stationary. i

A more specific object is to provide such device that is composed of a few number of parts to the end that the device is substantially maintenance free and is relatively inexpensive to produce.

The specific embodiment of the invention described in more detail hereinafter includes a housing in which is United States Patent ice journalled a shaft formed to be connected to a transmission at the speedometer cable connection thereof. The housing includes a connector for the speedometer cable so that the operation of the speedometer is not affected by addition to the vehicle of the apparatus of this invention. Mounted within the housing concentrically of the shaft is a cylindric drum that cooperates with the shaft through an overrunning clutch so that the drum is stationary when the vehicle is moving forwardly and rotates when the vehicle is backing. Mounted for cooperation with the cylindric drum surface is a flat spiral spring that has a circular portion frictionally engaging the cylindric drum surface and a spirally configured biasing portion that biases the circular portion generally in a direction of rotation corresponding to that of forward movement of the vehicle. Carried on the spring is a movable electric contact point which in cooperation with a fixed contact post mounted in the housing closes and opens a circuit in accordance with the direction of vehicle movement. Additionally, the spring is so arranged and configured that the contact will be opened when the drum is in a stationary state, a state occurring when the vehicle is stationary.

Other objects, features and advantages of the present invention will be more apparent after referring to the following specification and accompanying drawings in which:

FIG. 1 is a side view in cross section of the electrical actuator of this invention;

FIG. 2 is a cross-sectional view taken along line 22 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 at reduced scale and shows the apparatus when the vehicle is moving in a rearward direction;

FIG. 4 is a view similar to FIG. 3 showing the apparatus in a position when the vehicle has stopped after reverse movement; and

FIG. 5 is a view of a spring forming an important part of the invention, said spring being in a flattened condition in FIG. 5.

Referring more particularly to the drawing, reference numeral 12 indicates a housing for the apparatus which typically has an outside diameter of approximately 1% inches. The housing includes a mounting collar 14 which is threaded at 16 for engagement with a conventional vehicle transmission speedometer cable fitting, not shown. The opposite end of housing 12 includes an exteriorly threaded portion 18 for reattachment of the speedometer cable after the apparatus of the present invention is installed on the transmission. To afford convenient attachment of the housing to the transmission, collar 14 is rotatively supported on a bearing member 20, a split ring 22 being provided for retaining the collar onto the bearingmember. Bearing member 20 includes a circular flange 24 that is retained in housing 12 by a split ring 26. Bearing member 20 is centrally bored at 28 to rotatively support a shaft 30, the shaft having a journal 31 sized for running fit in the bore. Shaft 30 has a driven end portion 32 which is of square cross section or the like for receipt in a conventional transmission speedometer cable connecting fitting. Shaft 30 has on the opposite end thereof a longitudinally extending socket opening 34 that is complementary in cross-sectional shape to end portion 32 so that when the speedometer cable is reconnected to housing 12 by engagement with threads 18, the speedometer cable will be driven without interference from the apparatus of this invention.

Shaft 30 intermediate journal portion 31 and socket portion 34 includes a shoulder 36 which supports, for rotation with shaft 30, an overrunning clutch mechanism 38. cooperatively associated with the overrunning clutch is a sleeve member 40 that defines an internal cylindric surface 42. Sleeve member 40 includes an axial extension 44 that is bored at 46 for a running fit on journal 31 of shaft 30. Sleeve member 40 is thus rotatively supported with respect to shaft 30 and cooperates with overrunning clutch 38 so that when shaft 30 is driven in a direction corresponding to forward movement of the vehicle (clockwise as viewed in FIG. 2), sleeve member 40 will not be in rotative driving relation to'shaft 30; whereas when shaft 30 is driven in a direction corresponding to reverse or backing movement of the vehicle, overrunning clutch 38 will engage cylindric surface 42 so as to rotatively drive sleeve member 40.

Axial extension 44 of sleeve member 40 is formed with a cylindric outer drum surface 48 which is concentric with cylindric inner surface 42 and with the central axis of shaft 30. Thus, drum surface 48 is driven in a counterclockwise direction as viewed in FIGS. 2, 3 and 4 each time the vehicle to which the apparatus is mounted moves in a reverse direction. In one structure designed according to this invention, sleeve member 40 is formed of a thermoplastic resin such as that sold by E. I. Du Pont under the trademark Delrin. Such material is well suited for this purpose because in addition to its electrically insulative character, it has excellent bearing properties and a degree of surface lubricity.

Associated with drum surface 48 is a contact spring 50, the cylindric surface having an annular groove therein for supporting a split ring 51 to retain the contact spring on the cylindric surface. Contact spring 50 is constructed of electrically conductive resilient material, such as Phosphor bronze.

Contact spring 50 includes a substantially circular con volute portion 52 and a generally semi-circular spiral portion 54 that is integral with circular portion 52 and extends spirally outwardly therefrom in the direction corresponding to reverse movement of the vehicle. Spiral portion 54 functions to bias circular portion 52 in a clockwise sense as viewed in the drawing. Intermediate circular portion 52 and spiral portion 54 contact spring 50 is provided with an electric contact point 56 which is integral with the contact spring and which extends radially outwardly therefrom. The relative configuration of the components of contact spring 50 can be discerned from FIG. wherein the contact spring is shown in a flattened condition. As can be seen from FIG. 5, circular portion 52 includes a segment 58 adjacent contact point 56 that is of reduced width and functions to afford a degree of bend'ability between the circular and spiral portions of the spring.

Circular portion 52 of contact spring 50 is formed so that in a quiescent state it is biased into frictional engagement around the cylindric surface 48. Spiral portion 54 is formed on its free end with a bent out hook portion 60 and housing 12 includes rigid therewith a fixed post 62 for engaging the hook portion. Housing 12 also has a second fixed post 64 so spatially related with respect to electrical contact point 56 that the electrical contact point is circumferentially spaced from fixed post 64 in a rotative direction corresponding to forward movement of the vehicle when the spring is in an unstressed condition.

Fixed post 64 is electrically insulated from housing 12 by an insulative bushing so that a non-grounded conductor can be connected to the post. The other fixed post 62 can be similarly insulated from the housing, or alternatively, can be electrically connected to the housing. In the latter case, fixed post 64 will be grounded in response to rearward movement of the vehicle on which the apparatus is installed.

When shaft 30 is rotated in a direction corresponding to forward vehicle movement (clockwise in the drawing), insignificant torque is applied to sleeve 40 because overrunning clutch 38 does not establish a driving connection to cylindric surface 42 in such direction. Any torque applied to the sleeve tends to drive the sleeve in a clockwise direction as viewed in FIG. 2 so as to positively open the electrical path between contact point 56 and post 64. Clockwise movement of contact point 56 beyond the posi- 4 tion thereof depicted in FIG. 2 is prevented because any tendency for such clockwise movement causes circular spring portion 52 to engage more firmly drum surface 48 of sleeve member 40.

When the vehicle on which the apparatus is mounted moves in a rearward direction, see FIG. 3, sleeve 40 is driven in a counterclockwise direction as viewed in the figure, because in such direction a driving connection to the sleeve is established by the overrunning clutch 38. Due to the frictional engagement between circular spring portion 52 and drum surface 48, contact point 56 is moved counterclockwise to establish the circuit between the contact point and post 64. Thus fixed post 64, which is normally insulated from housing 12, is electrically connected to the housing through spring 50 and such phenomenon is used to establish an electrical circuit.

Continued reverse rotation of the sleeve in response to rotation of shaft 30 permits drum surface 48 to slide within circular spring portion 52, because such rotation of the drum surface tends to unwind the circular spring portion as a consequence of which the friction between the spring and the drum surf-ace is reduced so as to afford relative movement therebetween. Also contributing to relative movement between spiral portion 54 and circular portion 52 is a narrow spring segment 58, which both relieves the force between the circular spring portion and drum surface 48 and tensions spiral segment 54 to bias contact point 56in a clockwise sense.

Should rotative movement of the vehicle be terminated, but not reversed, both shaft 30 and sleeve 40 stop rotating but do not experience reverse movement to the position shown in FIG. 2. Termination of rotation, however, causes the electrical circuit through contact point 56 and post 64 to be interrupted. The force stored in spiral spring section 54 during the phase of operation described hereinabove in connection with FIG. 3 causes contact point 56 to move away from post 64 to so interrupt the circuit. The flexing that occurs at narrow segment 58 tends to reduce the area of frictional engagement between circular portion 52 and drum surface 48 (the space therebetween being indicated at 66) so as to permit a degree of movement of contact point 56 away from post 64. Such movement terminates when the force of friction between circular spring portion 52 and cylindric surface 48 increases to an amount equal and opposite to the biasing force of spiral spring segment 54, thereby stopping further clock wise movement of the spring contact point. From the stationary position as last described, contact point 56 will move to a closed position in response to further reverse movement of the vehicle or will move to the full open position as shown in FIG. 2 in response to forward movement of the vehicle.

More complete understanding of the invention can be had by restating the manner of operation thereof. When shaft 30 drives sleeve 40 in a rotative direction corresponding to reverse movement of the vehicle, the friction between drum surface 44 and circular spring portion 52 is suflicient to move contact point 56 into physical and electrical contact with fixed post 64. Simultaneous with such movement, energy is stored in spiral spring portion 54, which energy tends to bias contact point 56 in a clockwise direction away from fixed post 64. However, the force of friction between cylindrical drum surface 48 and the circular spring portion 52 together with the counterclockwise rotative movement of the drum surface 48 exceeds the force of the energy stored in the spiral spring portion. Accordingly, electrical continuity between contact point 56 and fixed post 64 exists so long as drum surface '48 rotates in the counterclockwise direction. When movement of the drum ceases in response to braking of the vehicle, counter-clockwise force on the spring terminates so that the force of the energy stored in spiral spring portion 54 is sufiicient to move contact point 56 out of contact with fixed post 64 by clockwise movement of the fixed contact point. Such clockwise movement continues until the force of the energy stored in spiral section 54 is exactly equal and opposite to the frictional force between circular spring portion 52 and cylindric drum surface 48, a condition depicted in FIG. 4.

Thus it will be seen that the present invention provides an extremely simple and compact device which responds to reverse movement of the vehicle on which it is installed, and which device establishes an electrical contact only when the vehicle is moving rearwardly. Moreover, the device of this invention can be installed on existing transmissions without in anyway interfering with conventional speedometer operation and because the entire structure is encased in a housing it is adapted to give long and trouble-free service.

While oneembodiment of the invention has been shown and described other adaptations and modifications can be made without departing from the true spirit and scope of the invention.

What is claimed is:

1. In combination with a member that is formed with a cylindric surface adapted to operate in a first state at which the cylindric surface rotates in a given direction and a second state at which the cylindric surface is stationary, apparatus for establishing an electrical circuit when the member is in the first state and for interupting the circuit when the member is in the second state comprising: a contact post fixed with respect to said cylindric surface and spaced radially therefrom, means defining a contact point associated with said contact post for establishing an electrical circuit when said point is in contact with said post, means for supporting said point for arcuate movement toward and away from said post, said point supporting means including a band substantially circumscribing said cylindric surface and in frictional engagement therewith so that said point is moved into contact with said post during said first state, and means for resiliently biasing said band in a direction tending to move said point away from said post, said biasing means affording a force in such direction less than a force on said point resulting from the kinetic energy of said cylindric surface and the friction between said band and said cylindric surface that tends to move said point toward said post so that when said cylindric surface is in said secand stationary state said biasing means interrupts the electrical contact between said point and said post.

2. The invention of claim 1 wherein said contact point, said point supporting band, and said resilient biasing means are integrally formed from flat conductive spring material and wherein said resilient biasing means is defined by a portion of said spring material extending spirally from said band and means for fixing the end of said spiral portion remote from said band with respect to said contact post.

'3. The invention of claim 1 including a portion of said biasing means being adapted to form a space between said band and said cylindric drum surface to reduce the frictional force therebetween, said means acting to form the area of said space in inverse relation to the proximity of said point to said post.

4. In combination with a member that is formed with a cylindric surface adapted to operate in a first state at which the cylindric surface rotates in a given direction and a second state at which the cylindric surface is stationary, apparatus for establishing an electrical ,circuit when the member is in the first state and for interupting the circuit when the member is in the second state comprising: a conductive spring associated with said cylindric surface, said spring including a first portion substantially circumscribing said cylindric surface and having a concave surface portion in frictional contact with said cylindric surface, a contact point extending radially from said first portion, and an outwardly spiralled biasing portion for resiliently biasing said contact point in a direction opposite the direction of rotation in said first state, said outwardly spiral portion extending in the direction of rotation and having the outer end thereof fixed with respect to said cylindric surface, and a fixed electrical contact post in circumferential alignment with said spring point and spaced apart therefrom in the second state, said fixed contact post being positioned for contact by said point in the first state.

References Cited UNITED STATES PATENTS 3,233,053 2/1966 Parks 200 --61.39

ROBERT K. SCHAEFER, Primary Examiner. M. GINSBURG, Assistant Examiner.

US. Cl. X.R. 340- 

